fix(update): export launcher virtualenv to uv

tests/hermes_cli/test_cmd_update.py

@@ -39,6 +39,45 @@ def mock_args():
     return SimpleNamespace()
 
 
+class TestCmdUpdatePip:
+    """Regression tests for pip-install update flows."""
+
+    @patch("shutil.which", return_value="/usr/bin/uv")
+    @patch("subprocess.run")
+    def test_update_pip_exports_virtualenv_from_sys_prefix(
+        self, mock_run, _mock_which, mock_args, monkeypatch
+    ):
+        from hermes_cli import main as hm
+
+        mock_run.return_value = subprocess.CompletedProcess([], 0, stdout="", stderr="")
+        monkeypatch.delenv("VIRTUAL_ENV", raising=False)
+        monkeypatch.setattr(hm.sys, "prefix", "/tmp/hermes-launcher-venv")
+        monkeypatch.setattr(hm.sys, "base_prefix", "/usr")
+
+        hm._cmd_update_pip(mock_args)
+
+        assert mock_run.call_count == 1
+        assert mock_run.call_args.args[0] == ["/usr/bin/uv", "pip", "install", "--upgrade", "hermes-agent"]
+        assert mock_run.call_args.kwargs["env"]["VIRTUAL_ENV"] == "/tmp/hermes-launcher-venv"
+
+    @patch("shutil.which", return_value="/usr/bin/uv")
+    @patch("subprocess.run")
+    def test_update_pip_does_not_export_virtualenv_for_system_python(
+        self, mock_run, _mock_which, mock_args, monkeypatch
+    ):
+        from hermes_cli import main as hm
+
+        mock_run.return_value = subprocess.CompletedProcess([], 0, stdout="", stderr="")
+        monkeypatch.delenv("VIRTUAL_ENV", raising=False)
+        monkeypatch.setattr(hm.sys, "prefix", "/usr")
+        monkeypatch.setattr(hm.sys, "base_prefix", "/usr")
+
+        hm._cmd_update_pip(mock_args)
+
+        assert mock_run.call_count == 1
+        assert "env" not in mock_run.call_args.kwargs
+
+
 class TestCmdUpdateBranchFallback:
     """cmd_update falls back to main when current branch has no remote counterpart."""